Headrest for a bathtub



FIG. 1 is a front perspective view of a headrest for a bathtub showing our new design;

FIG. 2 is a rear perspective view thereof;

FIG. 3 is a front view thereof;

FIG. 4 is a rear view thereof;

FIG. 5 is a right side view thereof, the left side view being a mirror image;

FIG. 6 is a top view thereof; and,

FIG. 7 is a bottom view thereof.

The broken lines shown in the drawings illustrate portions of the bathtub that form no part of the claimed design. 

CLAIM The ornamental design for a headrest for a bathtub, as shown and described. 